/*
* Copyright 2003 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.velocity.tools.view.i18n;
import java.util.Locale;
import javax.servlet.ServletContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.context.Context;
import org.apache.velocity.tools.view.context.ViewContext;
import org.apache.velocity.tools.view.tools.ViewTool;
/**
* <p>Allows for transparent content negotiation in a manner mimicking
* Apache httpd's <a
* href="http://httpd.apache.org/docs-2.0/content-negotiation.html">MultiViews</a></p>.
*
* <p>Reads the default language out of the ViewContext as
* <code>org.apache.velocity.tools.view.i18n.defaultLanguage</code>.
* See {@link #findLocalizedResource(String, String)} and {@link
* #findLocalizedResource(String, Locale)} for usage.</p>
*
* @version $Id: MultiViewsTool.java,v 1.3 2004/02/18 20:07:32 nbubna Exp $
* @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
*/
public class MultiViewsTool implements ViewTool
{
/**
* The key used to search initialization, context, and JVM
* parameters for the default language to use.
*/
protected static final String DEFAULT_LANGUAGE_KEY =
"org.apache.velocity.tools.view.i18n.defaultLanguage";
/**
* The two character abbreviation for the request's default
* language.
*/
protected String defaultLanguage;
/**
* Creates a new uninitialized instance. Call {@link #init}
* to initialize it.
*/
public MultiViewsTool()
{
}
/**
* Extracts the default language from the specified
* <code>ViewContext</code>, looking first at the Velocity
* context, then the servlet context, then lastly at the JVM
* default. This "narrow scope to wide scope" pattern makes it
* easy to setup language overrides at different levels within
* your application.
*
* @param obj the current ViewContext
* @throws IllegalArgumentException if the param is not a ViewContext
*/
public void init(Object obj)
{
if (!(obj instanceof ViewContext))
{
throw new IllegalArgumentException("Tool can only be initialized with a ViewContext");
}
ViewContext context = (ViewContext)obj;
Context vc = context.getVelocityContext();
defaultLanguage = (String) vc.get(DEFAULT_LANGUAGE_KEY);
if (defaultLanguage == null || defaultLanguage.trim().equals(""))
{
ServletContext sc = context.getServletContext();
defaultLanguage = (String) sc.getAttribute(DEFAULT_LANGUAGE_KEY);
if (defaultLanguage == null || defaultLanguage.trim().equals(""))
{
// Use JVM default.
defaultLanguage = Locale.getDefault().getLanguage();
}
}
}
/**
* Calls {@link #findLocalizedResource(String, String)} using the
* language extracted from <code>locale</code>.
*
* @see #findLocalizedResource(String, String)
*/
public String findLocalizedResource(String name, Locale locale)
{
return findLocalizedResource(name, locale.getLanguage());
}
/**
* Calls {@link #findLocalizedResource(String, String)} using the
* default language.
*
* @see #findLocalizedResource(String, String)
*/
public String findLocalizedResource(String name)
{
return findLocalizedResource(defaultLanguage);
}
/**
* <p>Finds the a localized version of the requested Velocity
* resource (such as a file or template) which is most appropriate
* for the locale of the current request. Use in conjuction with
* Apache httpd's <code>MultiViews</code>, or by itself.</p>
*
* <p>Usage from a template would be something like the following:
* <blockquote><code><pre>
* #parse ($multiviews.findLocalizedResource("header.vm", "en"))
* #include ($multiviews.findLocalizedResource("my_page.html", "en"))
* #parse ($multiviews.findLocalizedResource("footer.vm", "en"))
* </pre></code></blockquote>
*
* You might also wrap this method using another pull/view tool
* which does internationalization/localization/content negation
* for a single point of access.</p>
*
* @param name The unlocalized name of the file to find.
* @param language The language to find localized context for.
* @return The localized file name, or <code>name</code> if it is
* not localizable.
*/
public String findLocalizedResource(String name, String language)
{
String localizedName = name + '.' + language;
// templateExists() checks for static content as well
if (!Velocity.templateExists(localizedName))
{
// Fall back to the default lanaguage.
String defaultLangSuffix = '.' + defaultLanguage;
if (localizedName.endsWith(defaultLangSuffix))
{
// Assume no localized version of the resource.
localizedName = name;
}
else
{
localizedName = name + defaultLangSuffix;
if (!Velocity.templateExists(localizedName))
{
localizedName = name;
}
}
}
return localizedName;
}
}